Florence Williams is a contributing editor at Outside Magazine and a freelance writer for The New York Times, New York Times Magazine, Slate, Mother Jones, High Country News and Bicycling.

Courtesy of the author

When writer Florence Williams was nursing her second child, she read a research study about toxins found in human breast milk. She decided to test her own breast milk and shipped a sample to a lab in Germany.

What came back surprised her.

Trace amounts of pesticides, dioxin and a jet fuel ingredient — as well as high to average levels of flame retardants — were all found in her breast milk. How could something like this happen?

"It turns out that our breasts are almost like sponges, the way they can soak up some of these chemicals, especially the ones that are fat-loving — the ones [that] tend to accumulate in fat tissue," Williams tells Fresh Air's Terry Gross. "Unfortunately, the breast is also masterful at converting these molecules into food in the way of breast milk."

Learning that breasts soak up lots of chemicals made Williams wonder just what else was going on with breasts. A lot, as it turns out. In her new book, Breasts: A Natural and Unnatural History, Williams offers her take on — among other things — why breasts are getting bigger and developing earlier, why tumors seem to gravitate toward the breast, and how toxins from the environment may be affecting hormones and breast development.

She says many of those toxins, including the flame retardants found in her breast milk, may come from ordinary household items like couches and electronics, which often contain flame retardants. Some animal studies have shown that certain types of flame retardants interact with hormone levels.

"The flame retardants are known to react with the thyroid receptor, and it turns out that thyroid hormones are responsible for all kinds of important functions in our body, from neuro development in our brain to temperature and metabolism," she tells Gross. "We don't know at what levels these substances may be affecting humans, but it's certainly enough to make us stand back and say, 'Do we really need to have this furniture covered in flame retardants, or is there a better way here?' "

Breast Cancer

While researching her book, Williams also learned that more tumors form in the human breast than in any other organ in the body except for skin.

"The breast is not even fully developed until the last stages of pregnancy, and that's when the mammary gland forms," she says. "And for many years, breast tissues are sitting around not being fully differentiated. That's one of the theories about why the breast might be so vulnerable to carcinogens."

She says scientists are now studying whether the plastic additive BPA, which acts like the sex hormone estrogen, may be linked to cancer and reproductive problems in animals. Most plastic products, from package wrappers to water bottles, contain BPA.

"We know that if pregnant rats are dosed with BPA, their pups will grow up with altered mammary glands ... in ways that predispose that animal to breast cancer later on," she says. "A lot of people would say, 'A rat is a rat. It's not a human. What do we know about humans?' And we actually don't know that much. But recently a study just came out doing the same experiment but using Rhesus monkeys and, unfortunately, the results were very, very similar. Those monkeys ended up developing mammary glands that were altered by the chemical in ways that made it more likely to get breast cancer."

Williams says she likes plastics and wouldn't tell her kids to stay away from Legos, but she still cautions women in their child-bearing years against using an abundance of plastic products.

"I think we should be most concerned if we're pregnant or if we're lactating," she says. "But if we're beyond that — if we're a middle-aged man, for example — I think we can feel fairly comfortable that it's OK to keep using the yogurt containers."

Interview Highlights

On getting her daughter's urine tested to see what chemicals were in her body

"One of the ways in which modern life is changing our breasts is that they're showing up earlier in young girls. Young girls are developing breasts earlier than ever before. In fact, one-third of American girls start developing breasts by their ninth birthday. And this is earlier than even 15 or 20 years ago. ... There are some studies going on looking at why this is happening. And scientists are researching everything from these chemicals in girls' environments, to their lifestyles and exercise habits and diet, to social factors. ... As a way to discuss this, I thought it would be neat to test my daughter, who was 7 at the time, for some of the chemicals that are being looked at as possible culprits in the early puberty debate."

On driving oneself potentially crazy over toxins

"You can totally drive yourself crazy, and I don't recommend it. And that's one of the reasons I'm not so hypersensitive about trying to rid my house of these things. I just think, 'The anxiety isn't really worth it. It's not worth the health benefit.' ... We can only have so much control over the chemicals we're exposed to. As parents and as individuals, we can't really — in a meaningful way — affect our exposures. That made me realize that if we're going to live in a world where we feel a little bit safer or where we feel assured that chemicals are tested, we need to rely on our governments, on our manufacturers — the answers really seem to be upstream. We can't be our own filters. It's just impractical and almost impossible."

On how men are affected

"A lot of people are wondering if boys are being affected by these hormone-mimicking chemicals. And I guess the answer to that is that we don't really know definitively. But we are seeing an increase in male genital defects, and we're also seeing some young boys are showing up with increased breast tissue. So certainly it's an area for future inquiry."

On the benefits of breast-feeding

"We know far more about red wine than we know about human breast milk. But the things they're discovering are sort of amazing. We used to think that breast milk was just a food and that it was filled with fats and proteins and vitamins and that formula companies were successfully able to mimic this. But we now know that there are substances in breast milk that exist almost at the same levels that are not digestible by infants. So what are they doing there? It turns out, they're digestible by beneficial bacteria. So over millions of years, the mother has been creating a substance that will recruit useful bacteria into her infant's gut, and this sets her infant up for life. So as much as breast milk is a food, we also now understand that it's also a medicine."

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

TERRY GROSS, HOST:

This is FRESH AIR. I'm Terry Gross. We're going to talk about breasts. They're sexy. They're a source of pleasure. They're fetishized. They feed babies. They get made bigger and smaller through cosmetic surgery. They get cancer more than any other organ except the skin. Breast milk may have surprising toxins the mother has been exposed to, but it also has ingredients that are nearly medicinal for the baby.

These are some of the subjects of the new book "Breasts" by my guest, science reporter Florence Williams. She's a contributing editor to Outside Magazine. Florence Williams, welcome to FRESH AIR. Why did you want to write a book about breasts?

FLORENCE WILLIAMS: I set out down this path when I was nursing my second child. As a science journalist, I had seen some research that toxins were showing up in breast milk, and it sort of freaked me out. I was concerned about it. I wanted to learn more about it. And so I decided to test my own breast milk.

And what I learned amazed me on a number of levels. Among other things, I just learned that breasts kind of soak up a lot of chemicals. It made me wonder, well, what else is going on with breasts?

GROSS: So you sent in your breast milk to see what toxins might be in it. What did you find?

WILLIAMS: I shipped my breast milk to a lab in Germany, and the results came back with actually high to average levels of flame retardants in my breast milk, as well as trace amounts of pesticides, trace amounts of dioxin, which is a known carcinogen, and trace amounts of a jet fuel ingredient.

GROSS: OK, what was a jet fuel ingredient doing in your breast milk?

WILLIAMS: Yeah, exactly. That was my question. You know, it turns out that we just live these lives surrounded by modern industrial chemicals, and molecules get into our bodies through a number of different paths; through food, through water, through just touching substances. And then also we breathe them in.

And it turns out our breasts are actually - they're almost like sponges, the way they can soak up some of these chemicals, especially the ones that are fat-loving. The ones I mentioned tend to accumulate in fat tissue. And then unfortunately, the breast is also masterful at converting these molecules into food, in the way of breast milk.

GROSS: So you mentioned there were flame retardants in your breast milk. Where did they come from?

WILLIAMS: Well, I wanted to find that out also. So I did a number of studies regarding my own home. First, I studied my dust. It turns out that I guess I don't vacuum very often. I do have a lot of dust in my house, as do most of us, and it carries flame retardants.

So then I wanted to find out, well, how did the flame retardants get in my dust, whereupon I tore open one of my couches, and I biopsied it.

(SOUNDBITE OF LAUGHTER)

WILLIAMS: And this makes me laugh because you know we're living in a strange world where we have to biopsy our furniture. So I carved off a chunk of the foam, and I sent it to Duke University, and I did this for a number of household items, and it turns out, yes, there are flame retardants galore all over my household furniture.

GROSS: Is this couch that you mentioned that you bought, I won't mention the brand name, that smelled a lot when you bought it?

WILLIAMS: No, but it was from the same company.

(SOUNDBITE OF LAUGHTER)

WILLIAMS: And we were very surprised to find out that the flame retardant in that particular couch was one used sort of infamously in pajamas in the 1970s, and that was then phased out of pajamas. So people breathed a sigh of relief and thought phew, that flame retardant's gone because it was known to be mutagenic and cause birth defects.

But lo and behold, it turns out the flame retardant all along had just been transferred to our furniture.

GROSS: OK, so you found flame retardants, jet fuel. Anything else?

WILLIAMS: Let's see, trace amounts of pesticide, yeah.

GROSS: And was that DDT?

WILLIAMS: Yes.

GROSS: OK. So, you know, these are relatively small amounts, but, you know, a newborn is relatively small.

(SOUNDBITE OF LAUGHTER)

WILLIAMS: That's right.

GROSS: Newborns are tiny. So what are these small amounts of flame retardants, jet fuel, you know, DDT, what do they do to a little newborn baby?

WILLIAMS: Well, it turns out we don't know very much about the answer to that question, and so we have to look to the lab studies. It's much easier to test lab rats and mice for the effects of these chemicals than it is to test human infants. You know, infants are exposed to so many different things, not just through breast milk, I would say, but even more upsettingly through the umbilical cord and through the womb when, you know, the baby is really developing kind of most critically.

So I don't want to just blame breast milk for these problems, and I think it's also important to say that I did continue breastfeeding after I found out I had these substances. I was convinced that the benefits of breast milk still outweigh the risks. And of course formula, I should point, is not really perfect, either.

It has contaminants in it also, and, you know, depending on the water it's mixed with, it can also have things like heavy metals and pesticides in it, as well. But what I was able to find out is that at least in animal studies, some of these flame retardants and other endocrine-disrupting compounds interact with hormone levels and cause biological changes.

For example, the flame retardants are known to interact with the thyroid receptor, and it turns out that thyroid hormones are responsible for all kinds of important functions in our body, from neurodevelopment in our brain to temperature and metabolism, for example.

So we don't know at what levels these substances may be affecting humans, but it's certainly enough to make us stand back and say, do we really need to have this furniture covered in flame retardants? Or is there a better way here?

GROSS: So one of the things you learned in your research is that more tumors form in the breast than any other organ other than the skin, and skin is officially considered an organ. So any explanations for why that is?

WILLIAMS: Well, people are trying hard to find out. We don't really know what causes breast cancer. But one of the things that's so unique about the breast is that it's virtually the only organ in the body that does all of its developing and sort of growing up after infancy.

So for example, the breast is not even fully developed until the last stages of pregnancy, and that's when the mammary gland fully forms. And so for many, many years, in fact in modern women it's sometimes many, many decades, breast tissues are sort of sitting around not being fully differentiated. That's one of the theories about why the breast might be so vulnerable to carcinogens.

GROSS: What are some of the toxins that especially lodge in the breast tissues or the mammary glands?

WILLIAMS: So these are substances that are fat-loving, and of course they would also be attracted to other organs in our body such as the brain and the liver. But I think it's not as much fun to write a book about the liver, as it is to write a book about the breast.

But we do know that, for example, organochlorines, many industrial solvents, most pesticides - again, these flame retardants, which are all over the place, these are all compounds which are attracted to fat and end up residing in breast tissue.

GROSS: Now, you write about things like BPA, which is a product in a lot of plastics, phthalates, which are also found in a lot of plastics. And am I right in saying that both of these can be endocrine disrupters?

WILLIAMS: Yes, that's right. BPA, or Bisphenol A, is really known as the baby-bottle chemical. It's added to plastics to make it hard. Fortunately, it has been now phased out of most baby bottles. So that's the good news. But BPA was originally developed as an estrogen. It was designed to be taken by mothers to prevent miscarriage in the 1930s.

It wasn't actually used for that. It ended up being replaced by a chemical called DES, which you may have heard of. DES was a more potent estrogen that mothers took to prevent miscarriage, and unfortunately we now know that mothers who took that often gave birth to daughters who had - who suffered from serious reproductive cancers.

We also know that those girls whose mothers took DES also suffer a higher rate of breast cancer. So BPA, which was originally developed as an estrogen, is now a pervasive chemical. It's in everything from dental sealants to canned food linings to soda cans, to polycarbonate plastics. I think that my glasses probably have BPA in them. They're in grocery store receipts.

You know, and I had to ask myself, well, if we knew that this chemical acted as an estrogen, you know, why on Earth are we putting it in so many everyday products?

GROSS: So if it acts as an estrogen, and it becomes, it goes into your bloodstream, what does it do to your breasts?

WILLIAMS: That's a great question, and there have been some really interesting and kind of disturbing lab studies looking at that question. For example, we know that if pregnant rats are dosed with BPA, their pups will grow up with altered mammary glands, sort of mammary gland tissues that is a little bit denser in ways that predispose that animal to breast cancer later on.

And the BPA also appears to be changing the gene expression in the breast in a way that predisposes it to cancer. Now, a lot of people would say, well, a rat is a rat, you know, it's not a human. So what do we know about humans? And we actually don't know that much.

But, recently a study just came out a couple of weeks ago doing the same experiment but using Rhesus monkeys, and unfortunately, the results were very, very similar. Those monkeys ended up developing mammary glands that were really altered by the chemical in ways that made it more likely to get breast cancer.

GROSS: So when you found all of this out about how, like, BPA and phthalates can affect hormones and breast development, did you decide, well, I'm throwing out all the plastic in my house, I'm never going to buy plastic again, I'm never going to eat out of plastic again, changing my way of living. Did you do any of that?

(SOUNDBITE OF LAUGHTER)

WILLIAMS: You know, it's - I felt like it's really not my personality to tell my children they can't play with LEGO. You know, there are so many plastics in our environment, and I like plastic. You know, plastic has made my life great. You know, I use a plastic bicycle helmet. It's probably dripping with BPA, but I'm - no, I'm not about to get rid of it.

I think, you know, what helped me feel a little more reassured is that these chemicals do exist in our bodies in low levels, and I think we should be most concerned about exposure to them if we're pregnant or if we're lactating. But if we're beyond that, if we're a middle-aged man, for example, you know, I think we can feel fairly comfortable that it's OK to keep using the yogurt containers.

But you know, there are some things I don't do. I don't, for example, heat plastic in the microwave.

GROSS: So based on the research you did into what scientists know about what happens when chemicals lodge in the breasts or the mammary glands, are you convinced based on the evidence that you've read that this leads to breast cancer, that some of these new chemicals in plastic, some of the pesticides that we've developed in the past decades are responsible for, you know, the rise in the breast cancer statistics that we've seen?

WILLIAMS: I wouldn't feel comfortable at this point saying that the science is definitive enough. But what shocked me in writing this book was learning how few chemicals are ever tested for human health effects. And these studies and writing this book raised enough questions for me that I kind of have trouble believing that we really don't know what the effects of these chemicals are.

For example, even when some chemicals, the few chemicals we test for toxicity, often the researchers throw out the mammary gland. They will test, and they will dose an animal in infancy, and they'll dose an adult animal, but they won't dose, for example, an animal in puberty, which we now know to be one of the most sensitive times for the breast to have contact with carcinogens.

And so a number of breast cancer activists are arguing, I think, in a way that makes a lot of sense; that not only do we need to test the mammary glands of these lab animals, but we also need to test animals during puberty.

GROSS: If you're just joining us, my guest is journalist Florence Williams. Her new book is called "Breasts: A Natural and Unnatural History." Let's take a short break here, then we'll talk some more. This is FRESH AIR.

(SOUNDBITE OF MUSIC)

GROSS: If you're just joining us, my guest is Florence Williams. She's the author of the new book "Breasts: A Natural and Unnatural History." We talked earlier about shipping out some of your breast milk to a lab in Germany so they could tell you what chemicals that didn't belong in the milk were actually in the milk, and the results of that were kind of depressing.

Later you tested your urine and your daughter's urine to see what kind of chemicals were there that really didn't belong in the human body. Why did you want to test your daughter, as well as yourself?

WILLIAMS: One of the ways in which modern life is changing our breasts is that they're showing up earlier in young girls. Young girls are developing breasts earlier than ever before. In fact, one-third of American girls start developing breasts by their 9th birthday. And this is earlier than even 15 or 20 years ago.

Certainly when I was growing up - I think a lot of mothers my age out there talk about anecdotally the changes we see in third- and fourth-graders now. So there are some studies, interesting studies, going on looking at why this is happening. And the scientists are researching everything from these chemicals in girls' environments to their lifestyles and sort of exercise habits and diet to social factors. For example, there is some indication that girls growing up with a single parent may be more likely to enter into puberty earlier.

So as a way to discuss this, I thought it would be neat to test my daughter, who was 7 at the time, for some of the chemicals that are being looked at as possible culprits in the early-puberty debate.

GROSS: And what are some of those chemicals?

WILLIAMS: Those are chemicals like BPA, the baby-bottle chemical.

GROSS: Which we've talked about already in breast milk.

WILLIAMS: That's right. Also phthalates. There's also a class of chemicals known as parabens that are very commonly added to personal care products as preservatives. Let's see if there was another one. Oh, and then there's another chemical called triclosan, which I tested for. And that's used as an anti-microbial product. It's very, very commonly added to soaps. I think something like 77 percent of soaps now contain this chemical called triclosan.

GROSS: So this was a two-part study. You did the urine test for you and your daughter, and then you both detoxed for a week and did the study again. What were you trying to prove by detoxing?

WILLIAMS: I was interested to know how much control we have, whether it's possible to influence the chemicals that build up in our bloodstream. And part of that would tell us, you know, if we're getting these exposures where we think we're getting those exposures.

So for example, I stopped using a certain kind of toothpaste, you know, that I bought in the drugstore that's believed to have high levels of triclosan. And sure enough, I was able to drop my levels of triclosan about 99 percent just by stopping using certain personal care products.

GROSS: So what was the difference, all in all, for you and your daughter between the "toxed" and the detoxed urine tests?

(SOUNDBITE OF LAUGHTER)

WILLIAMS: Well, I was able to influence my levels more than I was able to influence my daughter's levels, and part of that is that I started at a higher baseline. For example, I drank more soda than she did during the "tox" phase. I sort of drew the line when it came to, you know, some of those things for her. And so I started at a higher point.

But I think one of the things that really surprised me about this experiment is that even after detox, when I virtually became a vegan and stopped eating all food that had ever touched plastic, I stopped riding in my car because my car upholstery is filled with some of these chemicals, I stopped using deodorant, and I stopped using really scented shampoos - you know, I did this sort of radical lifestyle change for three days, and despite that, there were some chemicals I was not able to influence very much at all. For example, some of the phthalates, which are these chemicals that bind fragrance. I still had high levels in my urine, and we just can't figure out where they're coming from. So I found that to be quite disconcerting.

GROSS: I imagine some of these chemicals stay in your system for a long time, whereas others probably get flushed out much quicker.

WILLIAMS: Well, most of these chemicals we were testing for have kind of known routes and timing for getting rid of them, and we knew that to be about 24 to 36 hours. So we accounted for that, actually, in the study, and we gave it enough time for my body to lose them.

And so there must be these other sources that we don't know about. For example, you know, I was thinking about my eyeglasses. You know, maybe I'm getting some BPA still from my eyeglasses, or maybe there's something in my roofing tile, you know, or in my office mouse or, you know, who knows. It's just - we just really don't know because companies are not required to label products.

We don't know which products have these things in them. You know, unless we have a basement laboratory, it's not like we can go down there and really deconstruct our toothpaste.

GROSS: Well, you know, you can drive yourself crazy because every single item in your home, in your office, in your car, in a taxi, in a bus, in a train can be potential enemies, potential toxins if you want to take this too far.

WILLIAMS: That's right. You can totally drive yourself crazy, and I don't recommend it. And that's one of the reasons that I'm not so, you know, hypersensitive about trying to rid my house of these things. I just think the anxiety isn't really worth it. It's not worth the health benefit.

GROSS: So tell us what your conclusions were from these double urine studies that you and your daughter did.

WILLIAMS: My conclusions were that it's surprisingly easy to get these substances into our body. It's pretty easy to get them out of our body. And yet despite that, it's not that easy. So it made me feel like we can only have so much control over the chemicals we're exposed to.

As parents and as individuals, we can't really, in a meaningful way, affect our exposures. And so that made me realize that, you know, if we're going to live in a world where we feel a little bit safer, or where at least we feel assured that chemicals are tested, we need to rely on our governments, we need to rely on manufacturers. The answer seems to really be upstream. You know, we can't be our own filters. It's just impractical and almost impossible.

GROSS: Florence Williams will be back in the second half of the show. Her new book is called "Breasts." You can read an excerpt on our website, freshair.npr.org. I'm Terry Gross, and this is FRESH AIR.

(SOUNDBITE OF MUSIC)

GROSS: This is FRESH AIR. I'm Terry Gross, back with science journalist Florence Williams, author of the new book "Breasts: A Natural and Unnatural History." When we left off, we were talking about chemicals that are absorbed into our bodies that may explain why many girls are developing breasts at an earlier age than girls in the past.

What are some of the other theories about what is causing girls to go through puberty and to start developing breasts at such a relatively young age?

WILLIAMS: Scientists are pretty confident in saying that the main driver of early puberty is related to diet. We know that one-third of children are now overweight or obese, and there seems to be a fairly strong relationship between body fat and the timing of puberty. However, many of the scientists I talked to said that it's simply not enough to explain the phenomenon. For example, there was a recent study in Denmark that looked at girls in terms of breast development and it basically replicated a study done 15 years ago. And the scientists found that girls are developing breasts one year earlier than they were just 15 years ago, and yet their body weight had stayed virtually the same. And so that scientist is really scratching her head. And she has a theory that the girls are somehow getting estrogen into their breast tissue that's not coming from within their bodies because they tested that, but it seems to be coming from other sources outside, for example, some of these chemicals that mimic estrogen.

GROSS: Which of those chemicals mimic estrogen?

WILLIAMS: A surprising number of chemicals mimic estrogen, it turns out. Some researchers here in the U.S. tested hundreds of common household plastics, broke them down, sort of tore them apart and put the solvent left over from the breakdown in a Petri dish full of estrogen-sensitive breast cancer cells. And they found that 90 percent of these common household plastics made these breast cells grow. So it turns out that, you know, this vast majority even of chemicals found in our kitchen turn out to be estrogenic.

GROSS: One of the things that amazes me about this is that I always believed in plastics as being inert substances, you know, unlike wood which, you know, can absorb water and that there's something really alive about wood. And it turns out, like, so many of these plastics are alive in the sense that they're almost like infecting us.

WILLIAMS: Well, plastics are really complicated. You know, there are these big composites of many, many different compounds and types of molecules and some of them, you know, are able to break apart pretty easily from the parent compound. And they do. Some of them are biologically active. It's very hard to imagine, even when we hold something - for example, a grocery store receipt - I think it's almost impossible for us to actually imagine that molecules from that receipt are getting into our bloodstream and lodging in our breast tissue. And yet, it turns out that's what's happening.

GROSS: And what's the chemical in the receipt that's lodging in our breast tissue?

WILLIAMS: That's the BPA.

GROSS: Hmm. OK. So all the chemicals we're talking about that can enlarge breast tissue and that can mimic estrogen, does this apply to men or just to women?

WILLIAMS: Oh yes, it does apply to men. That's a book I haven't written.

But, you know, a lot of people are wondering too if, for example, boys are being affected by these hormone-mimicking chemicals. And I guess the answer to that is that we don't again, really know, definitively. But we certainly are seeing an increase in some types of, for example, male genital defects, and we're also seeing some young boys are showing up also with increased breast tissue. So there are some things going on that concern researchers, and certainly it's an area for further scientific inquiry.

GROSS: And you've written about Camp Lejeune, in which there's a lot of toxins near the base and a relatively - a comparatively very high percentage of Marines there who have had breast cancer - male Marines I'm talking about, men.

WILLIAMS: That's right. Camp Lejeune is a large Marine base in North Carolina. It's recently been discovered that it had, for 30 years, the most contaminated public groundwater supply ever discovered in the U.S. It was especially filled with contaminants like benzene and vinyl chloride, trichloroethylene and perchloroethylene. These are chemicals that were mostly used as industrial solvents, for example, to clean military jeeps or used in the fuel depot. And these dribbled into the groundwater, contaminated the groundwater. And there are a number of people very, very sick, who at one time lived at Camp Lejeune and we're seeing all kinds of diseases coming out of there. But we're also seeing an emerging cluster of male breast cancer. There are now I think 73 or 74 men who have come forward with breast cancer.

Male breast cancer is an incredibly rare disease. It only occurs at about one percent the rate that it occurs in women. So when you have men showing up with it, especially young men, many of these men are in their 30s, 40s, 50s, it certainly has raised a lot of eyebrows. These men are great activists and they have helped convince Congress to help fund some very large health studies - $20-$30 million studies. So hopefully in a couple of years we'll know a lot more about the possible relationship between the male breast cancer and the chemicals showing up there.

GROSS: So getting back to your decision to continue breast-feeding, in spite of the fact that you found out that there were traces of toxins in your breast milk, what are some of the benefits of breast milk that convinced you you wanted to breast-feed?

WILLIAMS: Well, that was one of the funnest parts of writing this book is that I got to meet with this group of scholars who specializes in human milk. It turns out it's actually a very small group because there's far more money and research going into things like cow's milk and even red wine. We know far more about red wine than we know about human breast milk. But the things that they're discovering are sort of amazing. And one of them is that we used to think that breast milk was just a food and that it was filled with fats and proteins and vitamins and that formula companies were very successfully able to mimic this. But we now know that there are substances in breast milk that exist almost at the same levels that are not digestible by infants. And so what are they doing there? And it turns out that they're digestible by beneficial bacteria. So over millions of years, the mother has been essentially creating the substance that will recruit useful bacteria into her infant's gut and this sets her infant up for life. So as much as breast milk is a food we also now understand that it's also a medicine.

GROSS: It's creating the, what's the word? Bio...

WILLIAMS: The microbiome.

GROSS: The microbiome. Right...

(SOUNDBITE OF LAUGHTER)

GROSS: ... in the infant's digestive system. So you're helping to develop a healthy set of bacterial balance there. That's very interesting. What else did you find about breast milk?

WILLIAMS: Well, sort of related to that, I found out that when an infant is born it's what they call bacterially naive. It has no bacteria in its gut. And after birth within a matter of hours, bacteria start to sort of invade and colonize the infant. It's sort of a creepy thought, and it sort of makes sense, then, that the first substance you could give the child would be to help it, you know, regulate this onslaught and be able to manage it. And so that's why there are so many substances in breast milk that are able to fight pathogens that are able to, for example, kill E. coli on contact. The good bacteria comes in, following this breast milk, and it can out-compete the bad bacteria. So there's this amazing sort of tug-of-war going on right away and it's all mediated and facilitated by breast milk.

GROSS: And are these ingredients that aren't in formula?

WILLIAMS: Exactly. As you can imagine, the formula companies are falling all over themselves to try to replicate some of these substances. For example, oligosaccharides, which are complex sugars found only in human breast milk - these particular ones - formula companies would love to synthesize these, but they are at this point almost impossible to make.

GROSS: I know pharmaceutical companies would like to get onto this too.

WILLIAMS: Well, exactly. That's happening also. A number of biotech companies are trying to isolate and synthesize these compounds and market them not only to infants and toddlers in the Third World - who need the sort of extra immune boost - but also market them to adults in this country who might be immune-compromised or for whatever reason have an imbalance of bacteria. For example, cancer patients after treatment could really benefit from some of these substances in breast milk. It could be that pretty soon adults will be taking medicine based on breast milk.

GROSS: If you're just joining us, my guest is journalist Florence Williams, and she's written a new book called "Breasts: A Natural and Unnatural History." We'll talk more after we take a short break. This is FRESH AIR.

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GROSS: If you're just joining us, my guest is journalist Florence Williams. She's the author of the new book "Breasts: A Natural and Unnatural History."

Let's talk a little bit about the cosmetics of breasts. You write that breasts are getting larger and not just through breast enhancement cosmetic surgery, but they're just getting larger, and more manufacturers are making sizes like H and KK...

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GROSS: ...way beyond the traditional D. Why is that?

WILLIAMS: Well, one of the ways in which modern life is changing our breasts, is that our breasts are getting bigger and this is mostly attributed to the fact that our bodies are getting bigger in general, overall. You know, a lot of women gain weight in their breasts. Of course, men sometimes gain weight in their breasts too. And one of the more popular cosmetic surgeries now is male breast reduction surgery, believe it or not.

GROSS: So weight gain, obesity is part of the explanation for the larger bra sizes. Let's talk a little bit about cosmetic surgery. You say cosmetic breast surgery has become the most popular cosmetic surgery in the U.S. - ahead of nose jobs, eye lifts and liposuction. So you went to a plastic surgeon for an evaluation, just so you could see how they, you know, what the process is like, what women are told. Describe for us little bit about what you experienced during that evaluation.

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WILLIAMS: Yeah. I went to visit the plastic surgeon in Houston, Texas who performs more breast augmentations than anyone else in Texas, I think it's about 800 a year. And I'd describe his office as looking like a cross between Trump Plaza and Jiffy Lube. This incredibly beautiful office. It's seductive the minute you walk in. It's sort of white marble. They are these beautiful vases everywhere suggesting a curvaceous future, beautiful photographs of, sort of, Victoria's Secret-like looking women. And I had an evaluation. I said, you know, I'm a journalist but I want you to just treat me like I'm a patient and walk me through how this works. And so in the name of journalism, I disrobed. I took off my shirt and the doctor walked over with a tape measure and he measured me in every way you can imagine. He squeezed my breasts and he smushed them together. And he took a step back and he said well, let me just say you would be a perfect candidate for augmentation. So with that pronouncement, I then stepped into a 3-D imaging machine that took a 3-D picture of my, sort of, perfectly nice size-B breasts and simulated what they would look like with a size C or D implant in them.

And what the doctor told me is that I had this kind of regrettable ski slope going on on the upper part of my breast tissue, which I will say I had never noticed before as being a problem. But once the simulated implants were in and I looked at the new profile of my breasts, it looked more like an upside-down cereal bowl than like a ski slope.

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GROSS: So did this exercise in trying to, you know, experience with women who are having breast augmentation experience make you feel insecure about your breasts in a way that you hadn't before?

WILLIAMS: You know, I would say yes. I think that the plastic surgery industry is masterful at convincing women that what we have isn't really good enough. I think it's something that they have perfected over the years. In fact, when breast implants were first, when the silicone breast implant was first invented 50 years ago, plastic surgeons came up with a disease for small breast. They gave it a name, they called it micromastia, and said that women who had small breasts, you know, were really facing these very serious problems with their self-esteem later in life and they had these diseased breasts that weren't normal, that weren't womanly and a lot of women believed this.

GROSS: So what a lot of women do, apparently, a growing number of women, is have their breasts enlarged, mostly through implants?

WILLIAMS: Yes. Silicone implants are more popular now than ever before - 300,000 women a year get them. Implants today are a vast improvement over the first-generation silicone implants. They used to tear open quite often, and a sort of syrupy-like substance would migrate throughout the body. Women also faced problems with infection and, you know, a vast array of what they call aesthetic failure, or sort of visual complications in which sometimes the implants would migrate together and form something sometimes called uni-boob, or bread loafing.

And these problems still persist, actually, to some degree or another. Fortunately, the silicone bag holding the silicone gel is much stronger now and breast implants are less likely to rupture, but it still happens. And, of course, breast implants still get hard. It's known that breast implants have a shelf life of only about 10 years, so that women going in for this treatment are in effect buying into the need for repeated surgeries down the road.

GROSS: Do you have any idea of what the percentage of complications is for women who have breast augmentation surgery?

WILLIAMS: Yes. You know, the FDA banned silicone implants for about 14 years, from the mid-1990s until 2006. And as a condition for coming back on the market, it said that the major manufacturers had to do studies of side effects and complication rates. And so the first set of those studies was recently released, and it found, what I thought, rather shockingly high rates of complication: 40 percent complication rate within the first five years of implants, and between a 15 to 29 percent rate of reoperation within the first five years.

GROSS: So, you know, some women do breast augmentation for cosmetic reasons, and some women get implants because of cancer and because, you know, of the surgery that was done to remove the cancerous tumor. Is there a difference in outcome between those two different sets of women?

WILLIAMS: Yes. There is. About 20 percent of women who get implants are breast cancer patients, and they have much more complicated procedures. So the reason for some of that wide variation in complication rate is due to the fact that some of those women are breast cancer reconstruction patients for whom the surgery is much more complicated. And they have a much higher rate of failure and reoperation, unfortunately.

GROSS: So some of the women who have breast augmentation get the procedure done when they're pretty young, and they have yet to experience childbirth or breastfeeding and they still have many years of sexual activity ahead of them. How likely is breast augmentation to interfere with either the breast as a source of sexual stimulation, or of the breast as a functioning piece of equipment for breast feeding?

WILLIAMS: Yeah, that's a great question. One of the complications that can come out of implants is loss of nipple sensation. If you think about it, the nipple is one of the most sensitive parts of the body, and the reason is that nature really designed it this way because it has to be really sensitive when a baby is latching on. That's when all the hormones get released. That's when the milk has to come out.

So they're these wonderfully nerve-rich parts of the body, and yet sometimes during an implant surgery, the main nerve can be severed. So I saw a study that said 14 percent of women face nipple sensation loss. So, in a sense, you're taking this incredibly sexy organ that's incredibly sexually responsive and, in order to make it look sexy, you're actually killing the sexiness of how it feels, which seems ironic.

And then there's also sometimes a problem with lactation in women who have had implants. Some women have trouble lactating, and, again, that may be partly related to this loss of nipple sensation.

GROSS: So after doing the research for your book "Breasts: A Natural and Unnatural History," has it changed the way you feel about your own body?

WILLIAMS: Yes, it has. One of the profound realizations for me in writing this book was to learn how permeable our bodies really are. And what I mean by that is the kind of constant conversation that our cells are in with the world around us. Our bodies really pick up cues and substances from our environments, and these substances have the ability to affect our health, you know, in ways that I certainly hadn't thought about.

You know, I think I had this image of the human body, as many of us do, as being sort of like this temple. But really, the human body is more like a tree. It's permeable. It breathes. It interacts with these substances in our world.

GROSS: Well, Florence Williams, thank you.

WILLIAMS: Thank you. It's been a pleasure.

GROSS: Florence Williams' new book is called "Breasts." You can read an excerpt on our website, freshair.npr.org. Transcript provided by NPR, Copyright NPR.